<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>09_计算器练习</title>
</head>
<body>
<input type="text" placeholder="请输入数字1" id="i1"><br>
<input type="text" placeholder="请输入数字2" id="i2"><br>
<button onclick="calc('+')">加</button>
<button onclick="calc('-')">减</button>
<button onclick="calc('*')">乘</button>
<button onclick="calc('/')">除</button>
<h4>运算结果：<span></span></h4>
<script>
    function calc(o) {
        //1.获取输入框中输入的值，且转为数值类型
        let n1 = document.querySelector('#i1').value
        let n2 = document.querySelector('#i2').value
        n1 = parseFloat(n1);
        n2 = parseFloat(n2);
        //2.获取用来显示结果的span元素
        let spanE = document.querySelector('span');
        //3.根据运算符进行运算
        switch (o) {
            case '+':
                spanE.innerHTML = n1 + n2;
                break;
            case '-':
                spanE.innerHTML = n1 - n2;
                break;
            case '*':
                spanE.innerHTML = n1 * n2;
                break;
            case '/':
                if (n2!=0){
                    spanE.innerHTML = n1 / n2;
                }else {
                    alert('除数不能为0！')
                }

                break;
        }
    }
</script>

</body>
</html>